Rationale. The SCOR is highly dependent upon the generation and maintenance of transgenic and hybrid transgenic mice for the study of lung development and repair. The Animal Core is designed to take advantage of established expertise in the generation of the transgenic mice for the study of lung disease and in gene ablation studies that will be required for SCOR projects. Likewise, maintenance of germ-free, wild-type and transgenic lines will be critical in supplying genotyped mice for the various projects. This core will both generate the new transgenic lines and gene targeted mice, as well as maintain breeding and genotype analysis for the transgenic mice as required for the individual projeCts and investigators. This Core will: 1) provide animal husbandry, breeding, tail clip, Southern blot, PCR analysis for the mouse lines required for the SCOR projects; 2) generate all new transgenic lines described in the protocols by pronuclear injection and gene targeting; 3) facilitate maintenance, breeding, surveillance of the animal models; 4) produce mice exposed to carefully defined concentrations of oxygen for study of lung injury and repair. The animals will be maintained in sterile-barrier caging in a germ-free facility at the Children's Hospital Research Foundation under the direction of Gary Keller, D.V.M. This animal care program includes sentinel mice and careful ongoing serological and pathologic surveillance for identification of pathogens. Such surveillance will be critical in the evaluation of lung disease in our various transgenic models and be necessary for the interpretation of genetic vs. environmental effects on lung development and repair following injury.